1. Field of the Invention
The present invention relates to ink jet recording apparatuses and ink jet recording methods, and more specifically relates to an ink jet recording apparatus and an ink jet recording method in which preliminary discharge is performed.
2. Description of the Related Art
Hitherto, serial scan type recording apparatuses in which a recording operation is performed while a recording head scans over a recording medium have been commonly used for forming various types of images. In particular, ink jet recording apparatuses have recently come into widespread use because of their small size and ability to form color images easily.
In ink jet recording apparatuses, a plurality of nozzles are formed in a recording head, and recording is performed by discharging ink droplets from the nozzles.
In such ink jet recording apparatuses, nozzles to be used for discharging the ink droplets are determined in accordance with image data. Therefore, if there are nozzles which are not often used during recording, the ink with which they are filled evaporates and the viscosity thereof increases. In such a case, there is a risk that a normal discharge operation cannot be performed the next time the nozzles are used. In order to prevent this, a discharge operation called a preliminary discharge is performed even in unused nozzles at predetermined intervals of time. In the preliminary discharge, the ink is discharged toward an ink-absorbing hole (hereinafter also called a xe2x80x9cpreliminary discharge holexe2x80x9d) positioned at a region outside a recording area, so that the viscosity of the ink with which the nozzles are filled does not increase excessively.
On the other hand, in order to satisfy the recent requirements for high-resolution recording, a method has been suggested in which the resolution is increased by reducing the volume of ink droplets discharged from each nozzle and accordingly reducing the size of the dots formed. When the size of the ink droplets discharged from each nozzle decreases, the internal volume of the nozzles also decreases. Therefore, the amount of ink with which each nozzle is filled is reduced, so that the ink quickly evaporates and the viscosity thereof increases in a short time. As a result, the preliminary discharge must be performed more frequently at shorter time intervals. As the number of times the preliminary discharge, which is not directly relevant to the recording operation, is performed increases, the recording throughput decreases.
Accordingly, various suggestions for performing the preliminary discharge more efficiently have been made.
For example, according to Japanese Patent Laid-Open No. 06-115097, the preliminary discharge hole is formed at the same position as a run-up start position of a carriage in order to prevent the reduction in the throughput.
In addition, according to Japanese Patent Laid-Open No. 06-126982, in order to perform the preliminary discharge more efficiently, whether or not the preliminary discharge is necessary is determined by comparing the time elapsed since the previous preliminary discharge and the time until recording starts. In addition, according to Japanese Patent Laid-Open No. 07-266578, the preliminary discharge is more efficiently performed in the case in which the kinds of inks having different aridities are used. As described above, various suggestions for performing the preliminary discharge more efficiently have been made.
In addition, various kinds of methods for performing the preliminary discharge may be used in accordance with the conditions, and the time at which the preliminary discharge is performed may also be changed in accordance with the conditions.
Although the maximum recording width of many ink jet recording apparatuses is that of the A4 size, some ink jet recording apparatuses are capable of recording up to the A3 size. As described above, the preliminary discharge hole is positioned outside the recordable area in the scanning direction of the recording head. Accordingly, in recording apparatuses whose recording width is large, even when, for example, A4-size recording is performed, the recording head moves over a range corresponding to the A3 size or more when the preliminary discharge is performed. Therefore, recording speed is lower than that of recording apparatuses whose maximum recording size is A4 size.
In order to solve the above-described problem, Japanese Patent Laid-Open No. 05-069559 discloses an ink let recording apparatus in which preliminary discharge holes are formed at positions corresponding to size of recording media in addition to a home position and an opposite home position.
However, it is preferable not to provide a plurality of preliminary discharge modes since different preliminary discharge methods must be used and the control thereof becomes complicated.
In addition, when the preliminary discharge holes are formed at positions corresponding to paper sizes, the preliminary discharge hole to be used must be changed in accordance with the paper size. Therefore, the construction of the apparatus and scan control of the recording head become complex.
In view of the above, an object of the present invention is to provide an ink jet recording apparatus which is capable of performing preliminary discharge for maintaining the state of a recording head without a complex control process in order to record on different kinds of recording media in a manner suitable for each of them, which performs the preliminary discharge according to the size of the recording media without a complex mechanism, and with which a reduction in the throughput can be prevented.
According to one aspect of the present invention, an ink jet recording apparatus which records on a recording medium by moving a recording head having discharge outlets for discharging an ink and which performs preliminary discharges at a plurality of preliminary discharge positions, includes a preliminary-discharge-time setting unit which sets a time interval at which the preliminary discharges are performed; an elapsed-time counting unit which counts the time elapsed since the previous preliminary discharge of the recording head; and a comparing unit which compares a time determined on the basis of the elapsed time counted by the elapsed-time counting unit and the time interval set by the preliminary-discharge-time setting unit and outputs a preliminary discharge command when the elapsed time reaches the set time interval. A preliminary discharge is performed at a predetermined preliminary discharge position selected from the plurality of preliminary discharge positions by adjusting at least one of the set time interval and the time determined on the basis of the elapsed time.
In addition, according to another aspect of the present invention, an ink jet recording method by which an operation of recording on a recording medium is performed by moving a recording head having discharge outlets for discharging an ink and which performs preliminary discharges at a plurality of preliminary discharge positions, includes a preliminary-discharge-time setting step in which a time interval at which the preliminary discharges are performed is set; an elapsed-time counting step in which the time elapsed since the previous preliminary discharge of the recording head is counted; and a comparing step in which a time determined on the basis of the elapsed time counted in the elapsed-time counting step and the time interval set in the preliminary-discharge-time setting step are compared and a preliminary discharge command is output when the elapsed time reaches the set time interval. A preliminary discharge is performed at a predetermined preliminary discharge position selected from the plurality of preliminary discharge positions by adjusting at least one of the set time interval and the time determined on the basis of the elapsed time.
In addition, according to another aspect of the present invention, an ink jet recording apparatus which records on a recording medium by moving a recording head having discharge outlets for discharging an ink and which performs preliminary discharges at a plurality of preliminary discharge positions, the ink jet recording apparatus comprising a unit for switching a preliminary discharge position where the preliminary discharges are performed over the plurality of preliminary discharge positions in accordance with a recording mode.
According to the above-described construction, since the preliminary discharges are performed at the time interval set by the preliminary-discharge-time setting unit, the preliminary discharge hole can be selected in accordance with the recording medium by adjusting the time interval. This time interval is set to an adequate value by determining the time required for the recording head to reach a predetermined position above the recording, and predicting the movement of the recording head on the basis of the determined time.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments( with reference to the attached drawings).